1. Field
Exemplary embodiments of the present invention relate to a semiconductor designing technology, and more particularly, to a semiconductor device and a method for driving the same.
2. Description of the Related Art
A semiconductor device, such as a Dynamic Random Access Memory (DRAM) device, often includes a fuse circuit. A fuse circuit is a circuit for inverting a preceding option signal and outputting an inverted signal through a fuse programming process and is used to selectively provide an option signal in a voltage control circuit or a redundancy circuit.
The fuse programming process includes a laser blowing process and an electrical process. The laser blowing process is a method of cutting a fuse with laser beam. The fuse programming process using a laser may be performed in, for example, the wafer stage only before a fabricated semiconductor device is packaged. On the other hand, the electrical process is a method of changing the connection state of a fuse and performing a program operation in a packaged state of a fabricated semiconductor device. According to an example, anti-fuse may be used instead of a fuse.
An anti-fuse has opposite characteristics from a fuse, where an anti-fuse is set to a cut state in the initial stage of fabrication of a semiconductor device and after packaging, its state is switched to a connection state through a program operation. In other words, the anti-fuse starts out in the state of an insulator having as high electrical resistance as M ohms (Ω) in the initial stage of fabrication and is subsequently changed into a conductor having as low resistance such as a few hundreds of ohms (Ω) or lower through a program operation. Here, the physical change of the anti-fuse into a conductor is made by applying a voltage of a designated level or higher to the gap between electrodes, which are two conductive layers, and causing the insulator to be broken down.
FIG. 1 is a block view of a conventional anti-fuse circuit, and FIG. 2 is a block view illustrating an internal structure of a high voltage generation unit shown in FIG. 1.
Referring to FIG. 1, the conventional anti-fuse circuit 100 includes a substrate voltage generation unit 110, an anti-fuse unit 120, a driving unit 130, a high voltage generation unit 140, and a sensing unit 150. The substrate voltage generation unit 110 generates a substrate voltage VBBF. The anti-fuse unit 120 is coupled between an output node of the substrate voltage VBBF and a fuse state sensing node DN01. The driving unit 130 drives the fuse state sensing node DN01 with a high voltage VPP in response to a rupture control signal RUPEN. The high voltage generation unit 140 generates the high voltage VPP. The sensing unit 150 senses a resistance state of the anti-fuse unit 120 and outputs a fuse state sensing signal HIT.
The substrate voltage generation unit 110 may be realized as a charge-pump substrate voltage generation unit, which is described in detail below in connection with the high voltage generation unit 140.
Although the anti-fuse unit 120 is not illustrated in detail in the drawing, the anti-fuse unit 120 may be formed of an NMOS transistor including a gate coupled with the fuse state sensing node DN01, and a source and a drain coupled with the output node of the substrate voltage VBBF.
Also, the driving unit 130 may be formed of an inverter and a PMOS transistor. The inverter inverts the rupture control signal RUPEN and outputs an inverted rupture control signal. The PMOS transistor includes a gate for receiving an output signal of the inverter, and a source and a drain coupled between the output node of the high voltage VPP and the fuse state sensing node DN01.
The high voltage generation unit 140 may be implemented by a charge-pump voltage generation unit, which is described in more detail below with reference to FIG. 2. Referring to FIG. 2, the high voltage generation unit 140 includes a reference voltage generator 141, a voltage detector 143, an oscillator 145, and a pump 147. The reference voltage generator 141 generates a reference voltage VREFP having a designated voltage level. The voltage detector 143 detects a voltage level of the high voltage VPP in comparison with the reference voltage VREFP. The oscillator 145 outputs an oscillation signal OSC corresponding to a voltage detection signal DET that is outputted from the voltage detector 143. The charge-pump 147 generates the high voltage VPP in response to the oscillation signal OSC.
Hereinafter, the operation of the anti-fuse circuit 100 having the above structure is described.
First of all, the substrate voltage generation unit 110 generates the substrate voltage VBBF according to a target level, and the high voltage generation unit 140 generates the high voltage VPP according to a target level. Since the substrate voltage generation unit 110 and the high voltage generation unit 140 may each be realized as a charge-pump voltage generation unit, the high voltage generation unit 140 is representatively described herein as an example. First, when the reference voltage generator 141 generates the reference voltage VREFP corresponding to the high voltage VPP, the voltage detector 143 compares the reference voltage VREFP with the high voltage VPP so as to produce a comparison result and outputs the voltage detection signal DET corresponding to the comparison result. Accordingly, the oscillator 145 outputs the oscillation signal OSC, and the charge-pump 147 generates the high voltage VPP.
In this state, when the rupture control signal RUPEN is enabled at a desired timing, the driving unit 130 drives the fuse state sensing node DN01 with the high voltage VPP. Thus, the high voltage VPP and the substrate voltage VBBF are applied to ends of the anti-fuse unit 120, respectively, and the anti-fuse unit 120 is ruptured due to the voltage level difference between the ends.
Here, the sensing unit 150 senses the resistance state of the anti-fuse unit 120 and outputs the fuse state sensing signal HIT corresponding to the sensed resistance state. In other words, the sensing unit 150 detects that the anti-fuse unit 120 is ruptured when the resistance value of the anti-fuse unit 120 becomes lower than a target resistance value and outputs the fuse state sensing signal HIT corresponding to the detection.
Here, the anti-fuse circuit 100 having the above structure has the following features.
As mentioned above, the anti-fuse unit 120 is ruptured due to the voltage level difference between the ends of the anti-fuse unit 120. However, the rupturing may not be properly performed due to the conditions of process and voltage levels. In this case, an erroneous fuse state sensing signal HIT is outputted, and operation reliability of the anti-fuse circuit 100 deteriorates.